000
FXUS63 KLMK 150716
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
316 AM EDT Mon Apr 15 2024

...06Z Updated Aviation Discussion...

.KEY MESSAGES...

*   Isolated strong storms will be possible Monday afternoon.
    Locally gusty winds and brief hail would be the main threats.

*   Showers and thunderstorms are likely Tuesday night through
    Wednesday night. Multiple waves of strong storms are possible,
    with the greatest severe threat expected Wednesday afternoon and
    evening.

*   Significant cool-down appears increasingly likely next weekend.

&&

.UPDATE...
Issued at 922 PM EDT Sun Apr 14 2024

Current forecast remains on track with clouds developing over the
region during the night and low temperatures only falling into the
low 60s. As the front sinks south and the region heats, showers and
storms will be possible in the afternoon and evening. Strong storm
potential is conditional on the amount of heating. If clouds that
develop overnight are dense and do not scattered out in the morning,
this would limit instability. If clouds do scatter out, and the
region sees ample day time heating, strong storms could lead to
gusty winds and hail.

&&

.SHORT TERM /THROUGH TUESDAY/...
Issued at 335 PM EDT Sun Apr 14 2024

Tonight should be several degrees warmer than last night with a
light but steady southwest breeze given our position between high
pressure over Florida and a cold front draped from New England
through central Indiana to Colorado. Models show a significant
increase in 925-850mb RH, resulting in SCT/BKN cloud development
after midnight, especially east of Interstate 65...which will also
act to keep temperatures up. Low temperatures tonight should
generally be in the upper 50s and lower 60s...about 15 degrees above
normal.

On Monday the front to our north will slip slightly further
southward, to around the Ohio River. There`s not a lot of upper
support with this system, with 500mb winds weakening a bit in the
afternoon as heights rise and mid-level lapse rates decrease
slightly. Still, moisture, while not deep, will pool in the low
levels ahead of the surface boundary. Though the amount and
persistence of morning clouds will have an effect on temperatures,
at this time it appears that convective temperatures should be
easily surpassed as the atmosphere destabilizes diurnally. Most,
though not all, model solutions do show at least isolated storms
popping in the heat of the afternoon, which is consistent with some
model solutions from yesterday as well. So, will continue with low
PoPs in the forecast for Monday afternoon. Given the amount of
instability and moderate deep layer shear, some stronger storms
could develop, especially via any storm scale boundaries or
interactions. Straight hodographs and some dry air aloft support the
idea of gusty winds with the heavier storms. Progged wet bulb zero
heights, available shear, and and moderately wide CAPE on soundings
indicate brief periods of hail may be possible near the strongest
updrafts.

High temperatures tomorrow may be a bit tricky depending on how much
cloud we get. For now, with most of the region ahead of the front,
will go just on the high edge of the model mean with most locations
attaining lower 80s.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
Issued at 335 PM EDT Sun Apr 14 2024

Monday Night and Tuesday...

12Z hi-res guidance suggests that an area of isolated to scattered
thunderstorms will be ongoing at the beginning of the extended
forecast period Monday evening, with activity concentrated along a
quasi-stationary frontal boundary. This boundary is expected to
gradually lift north Monday night into Tuesday as a warm front, with
convection dwindling as instability diminishes. Rain chances will
linger into Tuesday morning for areas generally along and north of I-
64 as a narrow band of enhanced moist isentropic lift moves through
the area. Once this wave lifts into central IN, much of the daytime
hours on Tuesday should be dry across central KY and southern IN as
we should be far enough into the warm sector that high heights/warm
temperatures aloft should cap most if not all convection. Otherwise,
warm temperatures should continue in the presence of renewed
southerly flow, with highs Tuesday afternoon expected to reach the
upper 70s and lower 80s.

Tuesday Night through Wednesday Night...

The period of greatest concern for strong to severe storms across
the Ohio Valley will be Tuesday night into Wednesday night as a
negatively tilted upper trough ejects northeastward from the central
Plains into the upper Midwest, bringing an associated sfc cold front
through the Ohio and Tennessee valleys.

Tuesday night, ongoing convection across the mid-Mississippi Valley
is expected to move eastward into southwest IN and west central KY.
Medium-range deterministic guidance is now fairly consistent in
showing this wave of precipitation, with only subtle timing
differences of 3-6 hours between the models. While shear would
certainly be supportive of strong to severe storms with this first
wave, the region where the greatest low-level moisture and greatest
mid-level height falls (resulting in the greatest instability) is
located should be "outrun" by this wave of convection by the time it
reaches the CWA. As a result, the severe potential early Wednesday
morning will be determined by how long storms can survive in an
environment with little to no instability, and the threat will
decrease sharply from west to east across the region.

After a brief break Wednesday morning, a second wave of showers and
thunderstorms should arrive with cold FROPA Wednesday afternoon and
evening. With this wave, model soundings show greater instability as
the greatest low-level moisture and colder temperatures aloft should
be co-located across our area. Soundings Wednesday afternoon and
evening show around 1000 J/kg MLCAPE with strong deep-layer shear
and low-level helicity evident from wind profiles/hodographs. One
limiting factor for severe potential would be the antecedent wave of
showers/storms, which may limit moisture return and instability for
the second wave. As it stands, Wednesday afternoon and evening is
the more concerning of the two chances for severe weather, with all
convective hazards on the table. Showers and storms will clear the
area with cold FROPA Wednesday night into Thursday morning. The
areal flooding potential with Tuesday night into Wednesday night`s
showers and storms doesn`t look particularly impressive, as storms
should remain fairly progressive, and WPC only has portions of the
area outlined in a marginal ERO on Wednesday.

Late Week into Next Weekend...

Model agreement in the large-scale pattern remains relatively high
through the end of the week into next weekend. While the mid-week
cold front should pass far enough south of the region to bring a
brief reprieve from precipitation on Thursday, the parent trough
which is driving the system will de-amplify such that zonal flow
should set up across the Ohio Valley for the late week and early
weekend period. As subsequent shortwave disturbances transit within
this area of westerly flow, active weather should continue as
additional waves of precipitation are expected from Friday into the
weekend. Confidence in timing any one of these waves is fairly low,
with at least chance PoPs remaining in place at some point until a
larger trough clears everything out late next weekend. Temperatures
will gradually cool toward the end of the period as the broad
baroclinic zone sags slightly southward. By next weekend, below
normal temperatures are favored to return.

&&

.AVIATION /06Z TAFS THROUGH 12Z TUESDAY/...
Issued at 316 AM EDT Mon Apr 15 2024

Impacts/Confidence...
- Low to medium confidence in MVFR ceilings by midmorning
- Low confidence in thunderstorm coverage late this afternoon with
potential for low ceilings and reduced visibilities.

Discussion...Prevailing VFR conditions through the first morning
hours as a frontal boundary slowly moves to the region from the
north. As mentioned in the previous discussion, MOS and HREF
guidance have been hinting at SCT-BKN MVFR ceilings tonight via
moisture advection and weak forcing, but current trends do not
support that possibility so kept SKC through sunrise. On the other
hand, there is a higher probability for a brief period of MVFR
ceilings by midmorning as the cu field develops over the terminals.
Winds will generally blow from the west-southwest around 10 knots. A
more active period might be in store late this afternoon and early
evening as daytime heating triggers storms along the frontal
boundary. This activity should initially focus across central
Kentucky and move northward with time; however, there is low
confidence in coverage and exact timing.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
KY...None.
IN...None.

&&

$$

UPDATE...SRM
SHORT TERM...13
LONG TERM...CSG
AVIATION...ALL